The human heart is a hollow muscular organ having four pumping chambers for pumping blood; namely, the left and right atria, and the left and right ventricles. The heart further includes four one-way valves located at either the entrance or the exit of the four chambers. The heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Each of these valves is mounted in an annulus comprising dense fibrous rings attached either directly or indirectly to the atrial and ventricular muscle fibers.
Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Diseased heart valves may be categorized as either stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, and/or incompetent, wherein the valve does not close completely, causing excessive backward flow of blood through the valve when the valve is closed. Valve disease can be severely debilitating and even fatal if left untreated.
Various surgical techniques may be used to repair a diseased or damaged valve. In a valve replacement operation, the damaged leaflets are excised and the annulus is sculpted to receive a replacement valve. Another less drastic method for treating defective valves is through repair or reconstruction, which is typically used on minimally calcified valves.
Effective placement of a replacement valve in the tricuspid position is difficult due to the anatomical structure of the tricuspid valve. The tricuspid valve includes an annulus and three leaflets extending inward into the flow orifice defined by the annulus. Chordae tendineae connect the leaflets to papillary muscles located in the right ventricle to control the movement of the leaflets.
Located in the lower interatrial septum is the atrioventricular (AV) node, which is a section of nodal tissue that delays cardiac impulses from the sinoatrial node to allow the atria to contract and empty their contents first, and also relays cardiac impulses to the AV bundle. Because of the location of the AV node, cardiac surgeons must avoid placing sutures too close to or within the AV node when implanting replacement valves in the tricuspid position. Excessive pressure on the AV node can disrupt the normal function of the AV node.